Brainstorms are fun. Usually they involve getting a group of people into a room together, using some kind of white board or collaborative location to take notes and inviting participants to shout out their best ideas. Unfortunately, sometimes you’re faced with a creative challenge and can’t pull together a team of people to help you develop ideas. You’re on your own to solve it.

So, what can you do in this situation? Use images – or more specifically, use image search online. When I was in a similar situation trying to brainstorm concepts for the cover of my book last year, it was the combination of two images that led to the inspiration for the eventual award winning cover design. Searching for imagery works for most creative challenges, from a design oriented one like I had with my book cover, to a more executional brainstorm where you are trying to come up with marketing campaign ideas.

Here are four great tools that I use often:

iStockPhoto – This site has a wealth of photos, and most of them are available in a small size for just $1 in licensing fee. So not only can you use the collection of images, icons and graphics to get inspired, but if you happen to find one that you want to use for something, it won’t eat your entire budget.

Google Images– The most obvious and standard tool, Google Images can be good or bad for what you are looking for, and is rarely in between. Due to the huge collection of images that Google will return for just about any search, you are bound to find images that don’t match to your search very well. Sometimes this is good as it leads you in different directions, but other times the noise can win and the tool loses its usefulness.

Moodstream – A relatively new site from GettyImages, this is a very addictive online tool that lets you select particular moods based on several keywords and it will show you a stream of images to match that mood. If you are brainstorming based on emotions or more human terms, this could be the perfect tool to use.

Flickr – By far the largest photo sharing community on the web, I go straight to Flickr when I’m looking for more images of real life and real people as opposed to stock photography. You can often find more branded photos as well, which is really useful if you are trying to develop campaign ideas for a particular company or product.

Any other image search tools that you find really inspiring? Share them in a comment here and I’ll add them to the list.